Schmalenbach



MalCh l2, 1957 A. scHMALl-:NBACH 2,785,114

METHOD OF' EXTRACTION OF' HIGH-PERCENTAGE PRELIMINARY PRODUCT FROMBENzoLE-ENRICHED WASH 011 Filed Aug. 11, 1951 ,4001 F .5c/#m4 we A c# Af fof-wey nited METHOD QF EXTRACTGN 0F HIGH-PERCENT- AGE PRELIMINARYPRDUQT FRM BEN- ZGLE-ENRCEEB WASH OEL Adoif Schmalenhach, Essen,Germany, assigner, by messie assignments, to Kappers Company, lne.,Pittsburgh, Pa., a corporation of Delaware Application August 11, 1951,Serial No. 241,446

2 Claims. (Cl. Zim-46) The present invention relates to the extractionof a high-percentage of low boiling preliminary product from Wash oil,enriched with benzole and its homologues, from the by-product plants ofovens for the production of gas and coke.

The so-called preliminary product is obtained from wash oil charged withbenzole and its homologues, by treatment with steam. This preliminaryproduct, besides benzole and its homologues, contains greater or lesserquantities of naphthalene oil and wash oil fractions.

With a higher proportion of the low boiling benzole and its homologuesin the preliminary product, simpler apparatus and production processesare possible for obtaining motor benzole or pure benzole from thispreliminary product.

To obtain a so-called high-percentage of low boiling preliminaryproduct, i. e. one in which 95 to 98 percent thereof vaporises below 180C., it has previously been necessary to effect a two-stage distillation.In the majority of cases this was carried out by first preparing alow-boiling product by steam treatment of the enriched wash oil, andthen transforming this, partly in the vapour phase and partly in theliquid phase, by a second distillation into high-percentage preliminaryproduct. it has also been proposed to separate out a quantity ofhighboiling components, especially naphthalene oil, from the vapourmixture (which by itself only gives a low-percentage preliminaryproduct) in the refining apparatus by fractional condensation, so thatthe condensation of the remaining vapour produces a high-percentageproduct, whilst the condensate from the fractional condensation istreated in a special distillation apparatus to extract the benzolehydrocarbons and other valuable substances contained therein.

To obtain a high-percentage of low boiling preliminary product frombenzole-enriched wash oil by one-stage distillation only, it has furtherbeen proposed to effect fractional condensation of the high-boilingcomponents, namely the naphthalene oil, from the vapour mixturewithdrawn at the head of the refining apparatus, and to combine thiscondensate with the starting material, i. e. the benzole-enriched washoil, before its admission to the reliner. This method of operation ishowever accompanied by the drawback that the vaporisation of the Washoil in the reiiner is aided by the vaporisation of the naphthalene oilintroduced into the cycle. The result of this increased vaporisation ofWash oil constituents is that effective fractionation in the refiningcolumn is didicult or impossible, with the result that, on the one hand,the head product is poorer and on the other hand no naphthalene oilfraction can be Withdrawn from the refiner. Such withdrawal ofnaphthalene is however necessary in order to remove from the process thenaphthalene which is continually absorbed from the gases by the washoil, so as to maintain the wash oil in a condition for continuousabsorption of further benzole and its homologues from the gas.

2,785,114 Patented Mar. 12, 1957 The present invention, however,provides a way of producing from benZole-enriched wash oil, by a singlerelining or fractionating procedure, a high-percentage of low boilingpreliminary product by a continuous operation and with a high degree ofeconomy.

According to the invention the concentration of highboiling substances(naphthalene oil and certain wash oil components) at the head of thereiining column is increased, by recycling the same in heated conditionas hereinafter noted, so that the temperature of the resulting vapourmixture Withdrawn at the head of the column is higher than thecondensation point of steam, and the higher boiling components(naphthalene oil etc.) are extracted from the Withdrawn vapour mixtureby fractional condensation to such an extent that a high-percentage oflow boiling preliminary product can be directiy condensed from theremaining vapour mixture, whilst the condensate obtained by the primaryfractional condensation (which is composed in the main of naphthaleneoil and water, together with a certain amount of benzoie hydrocarbons)is heated, as hereinafter noted, e., to above the condensation point ofsteam, after removal of the water in a separator, and then isreintroduced into the refining column. Thus, in the process according tothe present invention, a continuous circulation of certain high-boilingsubstances is maintained, independently of the stream of wash oil,through the reiining column and a primary condenser connected to thehead of this column, with the result that a condensation of water and anincreased vaporisation of wash oil is impossible in the refining column,and this column can therefore effect a sharper separation of wash oilfrom the overhead vapor products.

The sharpness of separation can be substantially improved, and thisrepresents an important advantage of the present invention, by the factthat the ratio of recycled material in the column can be measurablyincreased as a result of the additional introduction of the preheatednaphthalene oil or the like from the primary condensation. By this meansit is possible, in accordance with a further feature of the invention towithdraw from the refining column, continuously or in batch fashion, anaphthalene oil fraction which is suliiciently concentrated to permitdirect crystallisation of naphthalene therefrom.

The process according to this invention presents particular advantageswhen used in combination with a continuous ow heater, of the so-calledpipe still type, for heating the benzole-enriched Wash oil (the startingmaterial) and the components from the primary fractional condensationdesigned for re-circulation. Hence, it is possible, in accordance with afeature of the invention, to eect the heating of the re-circnlatingcondensed component using the same pipe still as for heating thestarting material.

This may advantageously be carried out by arranging an additional systemof pipes, serving to heat the recirculating portion of the condensate,in the convection zone of the pipe still.

In accordance with a further important feature of the invention, theseparate heating of the re-circulating portion of the condensate canalso be utilised for the purification regeneration of the wash oil. Asis known, the wash oil in course of time undergoes an appreciablethickening, this being allied to a reduction in its absorptive capacity.Consequently it has hitherto been necessary to remove the wash oilcontinuously or batchwise from the gas purifying plant and replace it bya fresh Wash oil.

In accordance with this invention, spent Wash oil can be added to theportion of the condensate circulating through the refining column andthe primary condenser and, -advantageouslythe mixture heated in a pipestill to such a degreethat on expansion in a vaporising andV muckseparating chamber it is vaporised except for the pitchor resin-likeresidue of the spent or thickened wash oil.

rThus, by 'employing this featurerof the invention,it is unnecessary'towithdraw the wash oil from the plant or tov vregenerate itV bypurification inV a special 4distillation "apparatus, 'and the thickeningofthe oil can be continuously prevented andlthus the circulating washoil' maintained at a uniformly high absorptive level.

Further important features 'and advantages of the invention aredisclosed in the following description of a plant suited for carryingthe invention into effect, this being diagram'matically illustrated inthe accompanying drawing.

The cold;benzoleenrich`ed wash oil to be treated ows from a supplycontainer or the like (not shown) through Ya'pipeconduit Lirst through aheat-exchanger 2, where it is heated, and then through` a pipeY 3 to afurther heatexchanger 4, Afromwhichit'passes throughV a pipe line 5intro the first pipe system 6 of a pipe 'st-ill 7. These heatexchangers`2,4 also serve as co-ndensers for the vapour `mixture as is hereinafterdescribed. `The pipe system 6 ponents'llows away from the foot of column10 through the pipe line 12.

Ihe low boiling vapour mixture produced inthe column passes from the'topof the said column through the pipe line 13 into the heat-exchangerfi,which now acts as the primary condenser. In the latter the vapourmixture is brought to a temperature such that the naphthalene oil,

any wash oil components and the steam, together with a certain amount ofbenzole hydrocarbons, condense. This condensate flows through a pipeline 14 into a separating vessel 15 where'the water is taken ofrr fromthe remaining components. This water is taken Voff at 16,' whilst thewater-free condensate passes through a pipeline 17 into a container 18.From there it is forced by a pump 19 through a further pipe 20 into aheating pipe system 21 which is also arranged in the convection zone ofthe pipe lstill 7. Advantageously a partition wall 22 is providedbetween the two pipe systems 6 and 2l, so that regulated quantities ofheating gas can be brought into contact with each ofthe pipe systems 6and 21.

The heated high boiling oil product then passes through a pipe 23 to Iavaporizing and muck'separating chamber 24 in which it is expanded andthereby vaporised except for a pitch-like residue which iswithdrawn'through a Y line 25. The high boiling vapour mixture producedHows nally through a pipe line 26 into the refining column l0 at 27. VAscan be seen from the drawing, the point of highboiling admission 27 islocated at a higher part of the column than the admission inlet 28 forthe initial benzolized wash oil material.

The low boiling portion 0f the vapour extracted from the refining columnand not condensed in the primary condenser 4 ows through a pipe 29 tothe heat-exchanger 2, and thereafter to a `condenser 30 where the lowboiling volatile benzol mixture is completely condensed. The low boilingcondensate is collected in a container 31 and from thisY ahigh-percentage of low boiling preliminary product, containing about 95to 98 percent of constituents Vdistilling up to 180 C. can be drawn oitthrough a pipe line 32.

. Part of thel condensate fromthe reservoir 31 is passed a pump 33through aline 34 tothe head of the column I 10 at a point above thepoint 27.

`passing therewith through the pipe system 27 in the pipe still. Theused'washoilcomponent is also; evaporated inthe chamber 24, and pitch orresin Acontainedin" the used wash oil, which is responsible'forthethickening of the latter, is separated ol .as a residue.

To enable thetemperature in 'the' primary condenser 4 to be regulatedexactly tothe Yrequired value, a by-pass conduit 39, controlled by avalve 38, is arranged between the pipe lines 3 and 5. VBy appropriateadjustment of the valve 33 the amount of wash oil flowing through theprimary condenser 4 can be so regulated that the temperature of thevolatile mixture in the condenser 4 can be reduced accurately to theYlevel necessary-forme fractional condensation.

A practical example of a'methodcarried out inaccordance with the presentinvention-using apparatus Ycorrespending to the plant diagrammaticallyillustrated inthe drawing is as follows:

40,000 kg. of wash oil, containing 200 kg. water, kand at a temperatureof about V C., is passed per'hour through the pipe line 9'to therefining-column i0 from the pipe still 'i'. Approximately 640 kg. ofsteam per hour is admitted to the bottom ofthe reiiner 10-through thepipe 11.

The retining process is controlled so that 39,000 kg, of refined washoil is withdrawn per hour from the bottom of the column through the pipeline 12, whilst a/mixture of 5240 kg. of light oil and steam passesout'of the top of the refining column through the pipel 13. YIn theprimary condenser 4, 1000 kg'of condensate is withdrawn per hour and,after'being heated in the pipe systemv 2l of the pipe still to about 250C., is returnedto the retining column at 27 after passing through thepitchV extractor 24. At the same time 2400 kg. per hour Yof waterfreeddistillate is passed at about 30 C. from container 31, which containsthe liquid from the secondary condensers 2,- 30, to the head of thecolumn for recirculation. 1000 kg. of high-percentagerlow boiling lightoil (pre liminary product) is withdrawn per hour at 32.

What I claim is:

l. A Single distillation process for the continuous extraction of highpercentage of low boiling-preliminary product comprising benzole andhomologues boilingbelow naphthalene from benzole-enriched benzoleabsorbent wash oil which also containshigh boiling naphthalenecomponents, comprising: the steps ofintroducing wash oil enriched withbenzoleas aforesaid into a 'refining column partway up the sameandowingit downwardly therethrough eountercurrent'to direct steam to'remove bothsaid low boiling benzole components andt'said high boiling nap-hthalenecomponents fromthe entering wash oil, withdrawing both said low and highvcomponents as an overhead vapor mixtur'evfrom the head of the columnVat a point above the pointlof introduction of'the entering wash oilinto the column; maintaining lbetween 'the head of the column and a partof the'column loc-ated above the point of introduction of said wash oil;a'concentr'ation of said 4higher boiling components at a temperaturesuch that the temperature of the vapormixture'withdrawn overhead fromthe headV of the column is higher than'the condensation point of steam;fractionally condensing Said higher boiling naphthalene components fromthe low boiling benzole components of the Vapor mixture` so withdrawn asoverhead; returning said higher boiling'naphthalene componentcondensate, after freeing it of water and vaporizing it, to theY reningcolumn separately from the wash oil, at the-part'of the column locatedVabove Vthe wash oil inlet thereto but below the outlet for'overheadvapors vfrom the head of the column; Iand at a temperature in amountsuch as to maintain the temperature of the vapor mixture Withdrawn asoverhead at the head of the column higher than the condensation point ofsteam, and withdrawing naphthalene as an oil fraction from the column at-a point in the column above the inlet thereto of said returned higherboiling naphthalene component condensate but below the outlet at thehead of the column for withdrawal of said high and low boilingcomponents as overhead vapors from the column.

2. A process as claimed in claim 1, and which includes the further Stepsof adding spent wash oil into the high boiling naphthalene componentcondensate that is to be returned to the column, prior to vaporizing thesame, and thereafter vaporizing the naphthalene and wash oil from theirmixture leaving a pitch-like residue of the wash oil, and introducingonly the vapors of naphthalene and wash oil from said mixture to -thecolumn between the point of withdrawal of naphthalene as an oil fractionand the lower wash oil inlet to the column as aforesaid.

Koppers Dec. 2, 1919 Stevens Oct. 18, 1921 6 1,561,899 Barbet Nov. 17,1925 1,587,188 Schneible June 1, 1926 1,744,261 Cooke Ian. 21, 19301,744,421 Stroud et al. Ian. 21, 1930 1,839,894 Ricard et al. Ilan. 5,1932 2,054,096 Potts et al. Sept. 15, 1936 2,070,864 Ragatz Feb. 16,1937 2,100,922 Sachs Nov. 30, 1937 2,135,356 Schmalenbach Nov. 1, 19382,164,593 Rector July 4, 1939 2,196,878 Stover Apr. 9, 1940 2,290,373Lee July 21, 1942 2,299,283 Schmalenbach Oct. 20, 1942 2,342,145 Ishamet al. Feb. 22, 1944 2,342,165 Plummer Feb. 22, 1944 2,437,649 MilnerMar. 9, 1948 FOREIGN PATENTS 352,432 Germany Apr. 27, 1922 OTHERREFERENCES Chemistry of Coal Utilization, vol, II, chapter 28, (articleby Glowacki) pages 1136-1231, John Wiley Sons Publishers, 1945.

1. A SINGLE DISTILLATION PROCESS FOR THE CONTINUOUS EXTRACTION OF HIGHPERCENTAGE OF LOW BOILING PRELIMINARY PRODUCT COMPRISING BENZOLE ANDHOMOLOGUES BOILING BELOW NAPHTHALENE FROM BENZOLE-ENRICHED BENZOLEABSORBENT WASH OIL WHICH ALSO CONTAINS HIGH BOILING NAPHTHALENECOMPONENTS, COMPRISING: THE STEPS OF INTRODUCING WASH OIL ENRICHED WITHBENZOLE AS AFORESAID INTO A REFINING COLUMN PARTWAY UP TO THE SAME ANDFLOWING IT DOWNWARDLY THERETHROUGH COUNTERCURRENT TO DIRECT STEAM TOREMOVE BOTH SAID LOW BOILING BENZOLE COMPONENTS AND SAID HIGH BOILINGNAPHTHALENE COMPONENTS FROM THE ENTERING WASH OIL, WITHDRAWING BOTH SAIDLOW AND HIGH COMPONENTS AS AN OVERHEAD VAPOR MIXTURE FROM THE HEAD OFTHE COLUMN AT A POINT ABOVE THE POINT OF INTRODUCTION OF THE ENTERINGWASH OIL INTO THE COLUMN; MAINTAINING BETWEEN THE HEAD OF THE COLUMN ANDA PART OF THE COLUMN LOCATED ABOVE THE POINT OF INTRODUCTION OF SAIDWASH OIL, A CONCENTRATION OF SAID HIGHER BOILING COMPONENTS AT ATEMPERATURE SUCH THAT THE TEMPERATURE OF THE VAPOR MIXTURE WITHDRAWNOVERHEAD FROM THE HEAD OF THE COLUMN IS HIGHER THAN THE CONDENSATIONPOINT OF STEAM; FRACTIONALLY CONDENSING SAID HIGHER BOILING NAPHTHALENECOMPONENTS FROM THE LOWER BOILING BENZOLE COMPONENTS OF THE VAPORTMIXTURE SO WITHDRAWN AS OVERHEAD; RETURNING SAID HIGHER BOILINGNAPHTHALENE COMPONENT CONDENSATE, AFTER FREEING IT OF WATER